1. Field of the Invention
The present invention relates to a method of cleaning a template applied in imprint lithography and a pattern forming method using the template cleaned by the cleaning method.
2. Description of the Related Art
In recent years, a nanoimprint lithography has gained attention as a method of forming the micro-pattern. With the nanoimprint lithography, a resist pattern is formed by placing an imprint template formed with an a concavo-convex pattern in contact with a resist coated on the to-be-processed substrate and peeling the template from the resist after hardening the resist.
In releasing the template, part of the resist pattern is cut off, so that the resist may remain on the pattern face of the template in some cases. Therefore, in forming the pattern by the imprint lithography, it is required to appropriately remove the resist remaining on the template.
A method for removing the resist remaining on the template is described in patent document 1. Patent document 1 discloses a method in which a photo-catalyst such as titanium oxide is preformed on the pattern surface of the template, and when the resist residue occurs, ultraviolet ray is applied from the pattern face to oxidize and decompose the resist residue using the photo-catalyst action of titanium oxide and remove it, as shown in FIG. 3B of patent document 1. However, when titanium oxide is formed on the template, it is typically required to bake at a temperature of 500° or above, resulting in a problem that the pattern of the template is distorted, whereby this method is difficult in practice.
Also, a method for using the OH radical in order to make the resist surface hydrophilic is described in patent document 2. Patent documents 3 and 4 disclose a method in which the ultraviolet ray is applied to the resist pattern on the to-be-processed substrate from the side of the pattern face in the atmosphere containing water or oxygen to generate an OH radical or oxygen radical and remove part of the resist pattern using them to make the resist pattern slender.
[Patent document 1] JP-A-2005-327788
[Patent document 2] JP-A-2006-186111
[Patent document 3] JP-A-2006-32992
[Patent document 4] JP-A-2004-363444